Continuous wave
method of radio transmission, in which a sinusoidal carrier wave is switched on and off. Information is carried in the varying duration of the on and off periods of the signal, e.g. by Morse code
A continuous wave, or continuous waveform, (CW) is an electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration. It may refer to e.g. a laser or particle accelerator having a continuous output, as opposed to a pulsed output.
By extension, the term continuous wave also refers to an early method of radio transmission in which a sinusoidal carrier wave is switched on and off. This is more precisely called interrupted continuous wave (ICW). Information is carried in the varying duration of the on and off periods of the signal, for example by Morse code in early radio. In early wireless telegraphy radio transmission, CW waves were also known as "undamped waves", to distinguish this method from damped wave signals produced by earlier spark gap type transmitters.
Radio
Transmissions before CW
Very early radio transmitters used a spark gap to produce radio-frequency oscillations in the transmitting antenna. The signals produced by these spark-gap transmitters consisted of strings of brief pulses of sinusoidal radio frequency oscillations which died out rapidly to zero, called damped waves. The disadvantage of damped waves was that their energy was spread over an extremely wide band of frequencies; they had wide bandwidth.
Begin with the source’s own compact description: “Continuous wave” is method of radio transmission, in which a sinusoidal carrier wave is switched on and off. Information is carried in the varying duration of the on and off periods of the signal, e.g. by Morse code. The dossier treats that line as a proposition to test through Continuous, wave and method, not as a finished interpretation.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 15, 2026. The linked authority identifier is Q1129003. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Continuous wave” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.